Dungeons and Dragons

I was a bit unclear about the rules honestly, they seem ambiguous. It says that for the purpose of hiding, invisible creatures are heavily obscured, and any check requiring sight automatically fails. Perception doesn't require sight, but what other sense would it use out of earshot and smellshot? How far is earshot? I imagine it's gotta be pretty close for a naked creature using silent magic to fly. What would a failed stealth check even mean (how would they be detected), if they're downwind, invisible, flying, and their flight magic is silent? It also mentions attack rolls, but I don't see it mention stealth checks anywhere. But tbf I'm just going off roll20 - I find looking up special cases in the DMG painful (I have a hard copy, not searchable on roll20).

Wrt game types, were currently in the middle of a huge campaign, and so I can't change it right now. But I do really want to try Blades in the Dark (Forged in the Dark system). But there are plenty of D&D campaigns that don't have classic labyrinth style dungeons, even by WOTC. I compare, for example The Lost Citidel vs The Storm King's Thunder; the latter has very few labyrinthian dungeons, while the former is entirely labyrinths. They're dungeons, but of a different style, and I think that's ok.